Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Grand Forks ND
1252 PM CDT Sat Mar 28 2015
issued at 1237 PM CDT Sat Mar 28 2015
No update necessary.
Update issued at 944 am CDT Sat Mar 28 2015
Stratus lingering across the western forecast area so held clouds in longer
there. Otherwise no changes.
Update issued at 658 am CDT Sat Mar 28 2015
No changes to the grids for the morning update.
Short term...(today through sunday)
issued at 402 am CDT Sat Mar 28 2015
Winds today and tomorrow along with precipitation chances starting
tonight will be the primary forecast concerns.
The incoming shortwave trough is still digging onto the West Coast
but will progress quickly into the northern rockies today. Surface low
pressure currently over southern Alberta will move east and deepen
today...allowing for a pretty tight pressure gradient over the
region. 925mb winds are up close to 40 kts by late afternoon early
this evening...but with a warm air advection regime it may be
tough to get subsidence to help out with mixing. Went just below
Wind Advisory for now with a few spots in the northern valley
flirting with criteria. Think the greater threat for winds will
be late tonight and into tomorrow which will be discussed below.
Warm air advection and at least some sunshine should help temperatures
today warm well into the 40s.
Tonight...the upper shortwave will move out into the northern
plains...with the surface low digging across the County Warning Area into Minnesota. Models
continue to bring a fair amount of precipitation along the trough axis
and more precipitation wrapping around the cold side of the low. We will
not have the true instability that models show to our west for
this evening...but think there should be a good chance for shower
activity as the trough axis moves through. Given temperature profiles
think that any snow will hold off until Sunday morning and even
then it will be more of a mix. There will be a quick shot of cold
air advection on the backside of the surface low but then 850mb temperatures
return back above zero for Sunday afternoon with west to
northwesterly winds. Will continue to keep temperatures above average
with highs in the 40s to low 50s.
Model soundings show quite a strong mixed layer as the front comes
in early Sunday morning...with sustained winds above 30kts in some
areas. There should be good subsidence on the backside of the
system with cold air advection coming in...and winds aloft will
be strong. Think that Wind Advisory criteria is possible although
there are some uncertainties in the exact timing of the winds
coming into the area and how fast we get the pressure gradient
tightening. Will hold off on any advisories for the time being to
see what the 12z model runs show.
Long term...(sunday night through friday)
issued at 402 am CDT Sat Mar 28 2015
Sunday night through Monday night...northwesterly flow aloft sets
up with another weaker shortwave moving through...although there
are differences in the exact track of that wave. The European model (ecmwf) and Gem
take the system further south and have much of the County Warning Area with
precipitation...while the NAM and GFS are further north and just brush
our northern counties. Will continue to keep 20-30 probability of precipitation going
areawide for now. There should be a mix of rain snow during the
morning hours before we transition to all rain as temperatures warm
Monday afternoon. Think that at least the southwestern County Warning Area will
see some sun for part of the day so kept mondays highs in the low
60s with cooler readings further north and east. Light west winds
will help keep Monday night readings above the freezing mark in
Tuesday through Friday...long wave pattern is relatively zonal
with a Flat Ridge over the West Coast and high amplitude trough
over eastern North America. Pattern become more of a split flow.
Flat long wave trough develops over the West Coast by the end of
the period. Pattern remains progressive. The GFS is a slightly
faster solution than the European model (ecmwf). Little confidence after Wednesday as the
GFS and European model (ecmwf) become out of phase. Will blend the GFS and European model (ecmwf).
High temperatures were generally increased zero to five degrees for the
Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1245 PM CDT Sat Mar 28 2015
Low clouds across eastern ND this morning have been steadily
eroding. However...some a cumulus field has begun to develop across
parts of the area. Expect the cumulus thickening the most at kdvl
per NAM soundings/guidance. Believe ceilings will scatter out by late
afternoon however. Otherwise kfar and kgfk could see some low level cumulus
as well...but current line of thinking is only scattered coverage. Will
monitor and update if needed.
Tonight...it looks like two distinct periods of precipitation will move
through the area. Expect type to be rain but there is a slight
possibility that it could change to snow briefly right before
ending. Also...there is some weak elevated instability with the
first wave of showers...so lightning is not out of the question but
is rather unlikely. Another concern is the wind shift from the S to
the north-northwest and gusts to 35 kts possible late in the period.